Treatment of polymers to remove catalyst residues



United States Patent 3,012,022 TREATMENT OF POLYMERS TO REMOVE CATALYSTRESIDUES Hugh Wilma Boulton Reed and Robert Gilmour Jamieson Teller,Norton-on-Tees, England, assignors to Imperial Chemical IndustriesLimited, London, England, a corporation of Great Britain No Drawing.Filed Apr. 22, 1958, Ser. No. 730,057

Claims priority, applican'on Great Britain May 31, 1957 10 Claims. (Cl.26093.7)

This invention relates to the treatment of polymers.

Processes have been described for the polymerisation of unsaturatedhydrocarbons to high molecular weight solid polymers in the presence ofa metal-containing catalyst. Such a metal-containing catalyst may beformed by reacting a transition metal compound such as, for example,titanium tetrachloride, titanium trichloride or vanadium tetrachloridewith an organo-metal compound such as an aluminium alkyl, an alkylaluminium halide, a complex alkyl of an alkali metal and aluminium, e.g.lithium aluminium tetraethyl or an alkali metal alkyl. Thesepolymerisation processes may be carried out in the presence of an inertsolvent such as a hydrocarbon or in the presence of an excess amount ofthe unsaturated hydrocarbon monomer in the liquid phase and by the termsolvent as used hereinafter we include excess or unreacted unsaturatedhydrocarbon.

Examples of particularly valuable solid polymers produced by theprocesses mentioned above are polyethylene and polypropylene especiallythe so-called isotactic (crystalline) polypropylene.

The crude product of these processes is a solid polymer with occludedmetal-containing catalyst residues. The crude product is usually in theform of a slurry in an inert solvent or excess of the unsaturatedhydrocarbon. The solvent may contain atactic (amorphous) polymer insolution.

It is very desirable to remove these metal-containing catalyst residuesfrom the polymer, otherwise the polymer may be discoloured and mayundergo decomposition particularly when heated.

In previous Work, it was found possible to remove metal-containingcatalyst residues from solid polymers of unsaturated hydrocarbons bytreating the polymer with an amine in the presence of a solvent.

We have now found that this process is considerably facilitated if it iscarried out in the presence of an aluminium halide or an aluminium alkylhalide.

According to the present invention, therefore, there is provided aprocess for removing metal-containing catalyst residues from solidpolymers of unsaturated hydrocarbons which comprises treating thepolymer with an amine in the presence of a solvent and of an aluminiumhalide or aluminium alkyl halide, separating the solid polymer from thesolvent and recovering solid polymer.

A wide variety of amines which form complexes with metals may be used inthe process of the invention. Preferably the amine should be analiphatic primary amine which is appreciably soluble in the solvent.Examples of suitable amines are octylamiues, nonylamines, decylamines,tetradecylamines and octadecylamines. We prefer to use3,5,S-trimethyl-hexylamine.

The amount of the amine used depends upon the amount of metal-containingcatalyst residues in the polymer. Hence the amount of the amine may bevaried over a wide range. It is usually suflicient to use less than120%, particularly between 15% and 75% by weight of amine referred tothe weight of polymer insoluble in the solvent. However, if the amountof metal-containing residue is low, less than 15%, for example, 5%, byWeight of the amine may be used.

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It is preferred that the aluminium halide is soluble in the solvent.Examples of suitable aluminium halides are thus aluminium bromide andaluminium alkyl halides such as ethyl aluminium dichloride and ethylaluminium sesquichloride. vIt is preferred to use an aluminium alkylhalide.

Aluminium chloride may be used but since it is only slightly soluble inhydrocarbons it is desirable to use it as a solution in, for example,ether.

Suitable amounts of the aluminium halide or aluminium alkyl halide areup to 12% by weight of the polymer insoluble in the solvent. 2.5% and 5%by weight of the insoluble polymer.

It is preferred that the solvent is a hydrocarbon in which themetal-containing residues after treatmentwith the amine and thealuminium halide are soluble. The hydrocarbon may be an inerthydrocarbon used as a solvent in' the polymerisation process or it maybe the unsaturated hydrocarbon momomer which has been subjected to thepolymerisation process.

Particularly suitable solvents are parafdnic hydrocarbons such aspropane, butane, pentane and higher paraffinic hydrocarbons which are inthe liquid phase under the conditions of operating the process. Thecorresponding olefines such as propylene may also be used.

When the polymerisation process has been carried out in the presence ofa solvent for example, a saturated hydrocarbon, the amine and thealuminium halide may be added to the mixture of polymer andpolymerization solvent. Subsequently the solid polymer is separated fromthe solvent which may then be recovered for recycle to thepolymerisation process. I

Alternatively the solid polymer may be separated from the reactionproduct of the polymerisation process and then slurried in freshsolvent.

The aluminium halide or alkyl aluminium halide should preferably beadded to the mixture of polymer and solvent prior to the addition of theamine. The halide may be added as a finely divided suspension orpreferably as a solution in the solvent.

It is preferred that the process of the invention is carried out atmoderately elevated temperatures, preferably within the range 60 to C.

The process may be carried out under elevated pressures particularlywhen it is desired to use a solvent which is normally gaseous at thetemperature at which the process is operated.

After treatment with the amine and aluminium halide the solid polymer isseparated for example, by filtration, from the liquid components of themixture and Washed with a hydrocarbon which is preferably thehydrocarbon used as a solvent and very suitably a low boilinghydrocarbon such as propane or propylene.

The solid polymer may finally be steamed to remove the last traces ofsolvent.

Contact of the products of the polymerisation process with air andmoisture should preferably be prevented until the treatment with theamine and subsequent separation of the polymer and solvent has beencompleted. The use of an amine having anti-oxidant properties, in anamount such that residual amine remains in the polymer is of advantagein ensuring that no deterioration of the polymer due to oxidationprocesses occurs subsequently particularly during fabrication processesinvolving melting the polymer.

The process of the invention is applicable to the removal ofmetal-containing catalyst residues from polymers of unsaturatedhydrocarbons such as polyethylene and polypropylene produced in thepresence of a catalyst formed by reacting a titanium compound such astitanium tetrachloride or titanium trichloride with an organo-compoundof aluminium, e.g. an aluminium alkyl.

It is preferred to use between.

Example 1 1 gram aluminium trichloride in ml. diethyl ether was added to200 ml. of a suspension of polypropylene in petroleum ether containingw./v. suspended polymer. The polymer Was obtained by polymerisingpropylene in the presence of the reaction product of titaniumtrichloride and aluminium triethyl. The suspension had been stored forsome time and the original lilac colour of the freshly made suspensionhad partly discharged presumably due to contact with a limited amount ofair. The crude polymer contained about 1.0% ash.

The suspension was now heated at 75 C. for 30 minutes, 35 ml.3,3,5-trimethylhexylamine added and the temperature maintained at 75 C.for a further hour. The lilac colour of the suspension becamegrey-White. The suspension was filtered under nitrogen and washed with 1litre petroleum ether (boiling range 60 to 80 C.), under refluxconditions. White polypropylene was obtained which had an ash content of0.14% and which melted to give an almost colourlessmelt.

Example 2 3 grams methyl aluminium sesquichloride were added to 200 ml.of a slurry of polypropylene in petroleum ether (boiling range 60-80 C.)containing 25 grams suspended polypropylene. The crude polymer containedabout 1.0% ash.

The slurry was then heated at 70 C. for 1 hour and 30 ml.3,5,5-trimethylhexylamine added. The original lilac colour of the slurrywas discharged. Heating at 70 C. was continued for a further 10 minutes.The polymer was then filtered off and washed twice with 500 ml.petroleum ether at 70 C.

The final ash content of the polymer Was 0.16% and the polymer melted togive a pale yellow melt.

We claim:

1. In a process for removing catalyst residues from solid polymersprepared by polymerizing a member of the group consisting of ethyleneand propylene in the presence of a catalyst prepared by interacting amember of the group consisting of titanium tetrachloride and titaniumtrichloride with a member of the group consisting of aluminum alkyl andalkyl aluminum halides; the improvement comprising adding to a slurry ofsaid polymer in a solvent selected from a group consisting ofhydrocarbons and hydrocarbons mixed with ether, about 2.5-5 by weight ofthe polymer of a metal halide selected from the group consisting ofaluminum chloride, aluminum bromide and aluminum lower alkyl chlorides,adding a primary aliphatic amine having 8-18 carbon atoms, heating toabout 80 C. and separating said solid polymer from said solvent.

2. A process as claimed in claim 1 in which the hydrocarbon is aparafiinic hydrocarbon.

3. A process as claimed in claim 1 in which the hydrocarbon is theunsaturated hydrocarbon monomer used in the polymerization process.

4. A process as claimed in claim 1 in which the solid polymer afterseparation from the hydrocarbon solution is washed with a hydrocarbon.

5. A process as claimed in claim 1 in which the amine is3,5,5-trimethylhexylamine.

6. A process as claimed in claim 1 in which the amine is used in anamount less than 120% preferably between 15% and by Weight of thepolymer insoluble in the solvent.

7. A process as claimed in claim 1 in which said metal halide compoundis soluble in the solvent.

8. A process as claimed in claim 1 in which the polymer is finallytreated with steam.

9. A process as claimed in claim 1 in which the solid polymer ispolyethylene.

10. A process as claimed in claim 1 in which the solid polymer ispolypropylene.

References Cited in the file of this patent UNITED STATES PATENTS

1. IN A PROCESS FOR REMOVING CATALYST RESIDUES FROM SOLID POLYMERSPREPARED BY POLYMERIZING A MEMBER OF THE GROUP CONSISTING OF ETHYLENEAND PROPYLENE IN THE PRESENCE OF A CATALYST PREPARED BY INTERACTING AMEMBER OF THE GROUP CONSISTING OF TITANIUM TETRACHLORIDE AND TITANIUMTRICHLORIDE WITH A MEMBER OF THE GROUP CONSISTING OF ALUMINUM ALKYL ANDALKYL ALUMINUM HALIDES, THE IMPROVEMENT COMPRISING ADDING TO A SLURRY OFSAID POLYMER IN A SOLVENT SELECTED FROM A GROUP CONSISTING OFHYDROCARBONS AND HYDROCARBONS MIXED WITH ETHER, ABOUT 2.5-5% BY WEIGHTOF THE POLYMER OF A METAL HALIDE SELECTED FROM THE GROUP CONSISTING OFALUMINUM CHLORIDE, ALUMINUM BROMIDE AND ALUMINUM LOWER ALKYL CHLORIDES,ADDING A PRIMARY ALIPHATIC AMINE HAVING 8-18 CARBON ATOMS HEATING TOABOUT 60-80*C. AND SEPARATING SAID SOLID POLYMER FROM SAID SOLVENT.